I have recently run into two of these carrier groups in which the hole bored for the bolt tail was non concentric or too large in diameter. I have not been able to track down WIA as a Mfg., and this is the only marking to be found on these carriers. Does anyone know who made these?

I believe Wiltec, I'm also thinking DelTon is using them.

http://www.wiltecind.com/

http://www.wiltecind.com/news.htm

Thanks altopwescap. I checked their site, and it's a possibility, but I have replaced the two WIA carriers with DelTon carriers and have had no problems. DelTon gear seems to be first class. The WIA carriers are marked as such on the flat at the top front of the carrier, under the gas key. The two DelTon carriers have no markings. So, if Wil Tec is making the carriers for DelTon, they appear to be doing a very good job of it. Of course, these carriers could have been early production, which as we all know, can have problems. Although they both came in recently custom built M4's, they could have been early stock.